The present invention relates to apparatus useful to exchange heat and moisture in respiratory gas applications. More particularly, the invention relates to apparatus for heating and humidifying respiratory gases which exchange heat and moisture with respiratory gases, and preferably provide, e.g., generate, additional heat and/or moisture available to the respiratory gases.
During surgery and other medical procedures, a patient is frequently connected to an anesthesia machine or ventilator to provide respiratory gases to the patient. The respiratory gases passed to the patient are advantageously heated and humidified so that the gases entering the patient are of a suitable temperature and humidity so as not to adversely impact the patient. Heat and moisture exchangers (HMES) are often used to provide heat and humidity to the respiratory gases entering the patient. Typically, these HMEs are located so that respiratory gases from the patient pass through a tracheal tube into the HME, often a fibrous or other gas permeable material, which accumulates or collects heat and moisture from the exhaled gases. During the inhaling of respiratory gases, for example, from an anesthesia machine, the HME provides both heat and moisture to these respiratory gases prior to the gases entering the patient. Over a period of time, the HME is effective to maintain a certain level of temperature and humidity in the respiratory gases entering the patient.
Such HMEs do, however, have certain drawbacks. Thus, standard HME units currently commercially available are often less than satisfactory in delivering heat and/or moisture to the patient, for example, during the initial operation of the unit, and have configurations and structures which can cause clinician anxiety and patient trauma, for example, when the patient or HME unit is moved and the like situations. Also, during the initial or start up phase of the operation of a HME member, the amount of heat and moisture being exchanged out of the HME member to the respiratory gases being passed back to the patient is relatively low, for example, because the HME member is at a reduced temperature and a reduced moisture content. This xe2x80x9cstart upxe2x80x9d problem can adversely affect the patient. One approach to overcoming at least a portion of this problem is to provide the HME member with a hygroscopic component, for example, calcium chloride and the like components, which is effective to generate a limited amount of heat as the exhaled gases leaving the patient pass through the HME member. This provides a xe2x80x9cquick warm upxe2x80x9d HME member and at least provides a heated respiratory gas stream to the patient relatively quickly. However, the degree of humidification of the respiratory gases being passed to the patient still is relatively low during the first portion of the HME member operation, in part because of the water held by the hygroscopic component.
In addition, the inefficiencies of the typical HME member are such that a certain portion of the heat and moisture collected by the HME is lost, for example, to the environment, rather than being passed back to the patient by exchange with respiratory gases. The degree of heating and/or humidification of the respiratory gases varies over time which can adversely impact the patient.
In short, although the current commercial HME units provide certain benefits, they are not very user friendly to the patient.
It would be advantageous to provide apparatus by which respiratory gases can be effectively and reliably heated and humidified so that the comfort and safety of the patient is enhanced.
New apparatus for heating and humidifying respiratory gases have been discovered. Such apparatus provide for exchanging heat and moisture with respiratory gases exhaled by the patient and providing heat and moisture to the respiratory gases being inhaled by the patient. In general, the present apparatus are more patient friendly, that is provide for increased comfort and/or reduced trauma to the patient undergoing surgery or other treatment, than the current commercially available HMEs. Various features of the present invention provide enhancements as to the comfort and safety of the patient. Thus, the use of the present apparatus effectively provides heat and moisture to respiratory gases with reduced, if any, adverse effects on the patient. One important feature of the present apparatus is enhanced start up effectiveness so that the xe2x80x9cwarm upxe2x80x9d or xe2x80x9cbreak inxe2x80x9d time period of the system is reduced or even eliminated. These benefits are obtained with apparatus which are straightforward in construction, easy and relatively inexpensive to manufacture and use, and are effectively controlled to provide the results desired.
Generally, the present invention is directed to apparatus for heating and humidifying respiratory gases.
In one broad aspect of the present invention, apparatus for heating and humidifying respiratory gases comprise a housing, a filter element, and a gas permeable member. The housing has an inlet adapted for connection to a tracheal tube device and an outlet adapted for connection to a tube or tubes for passing respiratory gases, for example, to and from an anesthesia machine, ventilator and the like. The inlet and the outlet are positioned so that respiratory gases passing through the housing pass therebetween. The filter element is located in the housing and is adapted to filter respiratory gases passing through the housing. The gas permeable member is positioned in the housing between the inlet and the outlet and is adapted to exchange heat and moisture with respiratory gases passing through the housing. In general, the housing is designed to be compact and to reduce the amount of dead space between the tracheal tube device and the tube (or tubes) for passing respiratory gases. The compact housing allows the apparatus to be used and perform its functions more unobtrusively, relative to prior art HME devices. The reduced dead space increase the use efficiency of heat and moisture passing into and/or generated in the housing.
The present apparatus preferably are of modular design. This reduces manufacturing costs and provides performance benefits which inure to the patient. For example, the housing has an inlet portion including the inlet and an outlet portion including the outlet. The inlet portion of the housing is detachably secured to the remainder of the housing and is adapted to be replaced, preferably together with the filter element, while the outlet portion of the housing remains connected to the tube(s) for passing respiratory gases. This detachable or separable inlet portion of the housing is very effective in providing for reduced resistance to flow of respiratory gases through the housing. For example, after a period of time, material such as mucous from the patient tends to collect and/or settle on the filter element, creating a flow resistance. Rather than having to replace the entire apparatus, the inlet portion of the housing is removed, together with the filter element. A new inlet portion/filter element combination is substituted and the resistance to respiratory gas flow is reduced.
The filter element preferably is secured to the inlet portion of the housing. In one very useful embodiment, the inlet portion of the housing includes a first portion of a dogging assembly and the outlet portion of the housing includes a second portion of the dogging assembly positioned to matingly engage the first portion to detachably secure the inlet portion to the outlet portion of the housing. The inlet portion of the housing preferably includes a peripheral ring or rim extending radially outwardly of the first portion of the dogging assembly. This peripheral rim is adapted to prevent the inlet portion of the housing from snagging other objects, for example, on the patient in the operating or treatment room. This feature allows for movement of the apparatus on or about the patient without the apparatus being snagged or otherwise caught up on such other objects. This feature advantageously reduces the risk of the tracheal tube connection to the patient being disturbed by such movement and, thus, reduces the risk of trauma to the patient.
In another useful embodiment, the outlet portion of the housing is rotatable relative to the inlet portion of the housing. For example, the housing may include an intermediate portion located between the inlet portion and the outlet portion of the housing. The outlet portion includes a first groove and the inlet portion includes a second groove positioned and adapted to matingly engage the first groove to rotatably secure the outlet portion to the intermediate portion. This rotation or swiveling between the various components of the housing allows for movement of the apparatus or reorientation of the apparatus with reduced risk of disturbing the tracheal tube in the patient by such movement.
A very useful embodiment provides that the housing includes a first intermediate portion, and that a generating material is located in this first intermediate portion. This generating material is adapted to generate water available to humidify gases passing through the housing. The first intermediate portion of the housing is detachably secured to the outlet portion of the housing. Further, the apparatus preferably includes an additional amount of generating material located in the housing adjacent the generating material noted above. This additional amount of generating material is adapted to be replaced while the first intermediate portion is detached from the outlet portion and the outlet portion remains connected to the tube(s) for passing respiratory gases. By replacing the additional amount of generating material, the effective useful life of the apparatus can be extended.
In one embodiment, the present apparatus preferably includes a fitting joined to both the housing and the tracheal tube device. The fitting defines a gas flow path which is substantially perpendicular to the flow path of respiratory gases passing through the housing.
In another useful feature of the present apparatus the inlet is rotatable relative to the remainder of the housing. For example, the inlet includes an open end away from the tracheal tube device having an outwardly extending annular flange. The housing includes an upwardly extending annular projection located in proximity to the outermost end of the flange. A ring member, preferably secured to the housing, is positioned so as to capture the projection and prevent the flange from separating from the housing. In addition, the ring receives the annular flange so that the annular flange is rotatable relative to the remainder of the housing. A fitting is preferably joined to both the inlet and the tracheal tube device and has a gas flow path which passes through an angle of about 90xc2x0, for example, is an elbow-like fitting.
In yet another broad aspect of the present invention, the apparatus comprise a housing, generally as described herein, a baffle assembly, and a gas permeable member, generally as described herein. The housing includes an inlet which defines an inlet passage. The baffle assembly is positioned so as to be effective in reducing the kinetic energy of mucous passing from the tracheal tube device. Reducing the kinetic energy of such mucous causes the mucous to collect relatively closer to the periphery of a housing member, thereby prolonging the useful life of the present apparatus. The baffle assembly preferably includes two spaced apart sets of baffles extending from the housing to the inlet passage. A fitting preferably is included and is joined to both the housing and the tracheal tube device and the baffle assembly is located in the fitting. The fitting preferably defines a gas flow path which is substantially perpendicular to the flow path of the respiratory gases through the housing. The baffle assembly, in one embodiment, includes two spaced apart sets of baffles extending inwardly from the fitting into this gas flow path.
In a very useful embodiment, the spaced apart sets of baffles define a guide path through the fitting sized to allow an elongated member, such as a catheter and the like, to be passed therein in treating the patient, for example, in removing mucous from a patient, through the tracheal tube device. The fitting includes one opening connected to the tracheal tube device and may include a second opening, preferably a substantially opposing second opening, through which respiratory gases can be sampled. A filter element, as described herein, preferably is included and is located in the housing.
The housing preferably includes a through port through which mucous from the tracheal tube device having passed across the baffle assembly is removed from the housing. This approach is particularly effective because the baffle assembly has reduced the kinetic energy of the mucous causing it to collect or pool near the periphery of the housing. The port, which is located to have access to the inner periphery of the housing, is effective in removing such mucous, for example, using a conventional suctioning device. Removing such mucous results in advantageously increasing the effective useful life of the apparatus.
In a further aspect of the invention, the apparatus comprise a housing, as described herein, a gas permeable membrane, as described herein, and an amount of generating material, as described herein. The generating material, such as a carbon dioxide absorbing material and the like, is positioned in the housing so as to prolong the effectiveness of, that is to extend the effective useful life of, the generating material to generate water relative to an identical amount of the same generating material positioned as a layer of uniform thickness across substantially the entire flow path of respiratory gases passing through the housing from the inlet to the outlet.
One advantage of such an apparatus is to allow useful humidification enhancement to the respiratory gases over a relatively long period of time, for example, during long surgical procedures. The present apparatus, in effect, makes more efficient or effective use of the generating material by positioning the generating material in the housing as other than a layer of uniform thickness across substantially the entire flow path of the respiratory gases passing through the housing from the inlet to the outlet. For example, in one embodiment, the generating material is positioned as a layer of non-uniform thickness across substantially the entire flow path of the respiratory gases passing through the housing from the inlet to the outlet. Thus, for example, the layer of generating material may include a peripheral region having a first thickness and a central region having a second thickness which is greater than the first thickness.
In a particularly useful embodiment, a valve assembly is provided in the housing and is adapted to cause a portion of the respiratory gases passing through the housing from the inlet (adapted for connection to a tracheal tube device) to the outlet (adapted for connection to the tube or tubes for passing respiratory gases) to bypass the generating material. Such bypass effectively extends the useful life of the generating material in the present apparatus. The valve assembly preferably is further adapted to cause all the respiratory gases passing through the housing from the outlet to the inlet to contact the generating material. Thus, gases which are exhaled from the patient partially bypass the generating material, whereas gases which are inhaled by the patient are routed so that all such gases contact the generating material. This provides an effective use of the generating material while, at the same time, minimizing the amount of moisture which is lost, for example, is condensed or otherwise passed outside the housing, and unavailable to the patient.
Yet a further aspect of the present invention is directed to apparatus which comprise a housing having an inlet portion and an outlet portion, as described herein, a filter element, as described herein, a gas permeable member, as described herein, and a humidification member. The humidification member is separate from the filter element and the gas permeable member and is located in the housing. This humidification member is adapted to receive moisture supplied from outside the housing and to transfer the moisture to respiratory gases passing through the housing.
The housing preferably includes a port through which moisture is supplied to the humidification member. The humidification member preferably is located closer to the outlet then the filter element and/or the gas permeable member. Although any useful material can be employed as the humidification member. It is preferred that it be a hydrophilic polymeric material or, more preferably, a hydrophilic open cell foam material.
In another broad aspect of the present invention, the apparatus comprise a housing, as described herein, a gas permeable member, as described herein, a generating material, as described herein, and a hygroscopic component positioned in the housing separate and apart from the gas permeable and the generating material. The hygroscopic material, such as calcium chloride and the like, is adapted to generate heat available to heat respiratory gases passing through the housing. The use of a separate hygroscopic component effectively provides a very quick heat input to the respiratory gases being passed to the patient without adversely interfering with the operation of the other components in the housing. Such a hygroscopic component very effectively reduces trauma and increases patient comfort, particularly during the start-up of the present apparatus.
Preferably, the hygroscopic component is positioned between the outlet and the gas permeable member, and the generating material is positioned between the inlet and the gas permeable member. This arrangement of materials within the housing very effectively uses moisture which might otherwise be lost down the exhaled gas tubing (and, thus, unavailable to the patient) to interact with the hygroscopic component produce heat to warm respiratory gases which are passed to the patient. Thus, moisture which may condense or otherwise be lost to the patient is, in effect, converted to very useful and welcomed heat which warms respiratory gases passed to the patient, for example, on the next inhalation breath. The patient is provided with this heat benefit from moisture which would otherwise be lost to the patient.
One additional broad aspect of the invention is directed to apparatus which include a housing, as described herein, a gas permeable member, as described herein, and a cover member secured to the housing and effective to reduce heat loss from the housing. In a very useful embodiment, the cover member includes a heat generating material effective to provide heat to the housing, and ultimately to the respiratory gases passing through the housing. The heat generating material preferably is effective to generate heat in response to being exposed to oxygen.
In one useful configuration, the cover member further includes a cover shell positioned so that the heat generating material is located between the cover shell and the housing. This is very effective in maintaining the heat generating material in place and, at the same time, preferably acts to direct the heat generated toward the housing. The cover shell preferably is structured to allow the heat generating material to be exposed to oxygen.
One further broad aspect of the invention provides apparatus which comprise a housing, as described herein, a gas permeable member, as described herein, and an amount of heat generating material located in the housing between the inlet and the outlet and adapted to generate heat available to warm respiratory gases passing through the housing. The heat generating material is effective to generate heat independent of water generation and water present in respiratory gases passing through the housing. Preferably, the heat generating material in the housing is effective to generate heat in response to oxygen present in respiratory gases passing through the housing.
In one embodiment, the heat generating material in the housing is positioned separate and apart from the gas permeable member. Alternately, the heat generating material can be located within or combined with the gas permeable member. The heat generating material preferably is provided so as to control the amount and rate of heat generation from the heat generating material. For example, the heat generating material may be coated with a hydrophobic, oxygen permeable substance effective to reduce the deleterious effect of the water in the housing on the heat generating material. In other words, the heat generating material preferably is configured so that the other components within the housing have a reduced, or even substantially minimal, effect on heat generation.
In one embodiment, the apparatus further comprises a water, preferably liquid water, delivery assembly containing water and located in the housing. The water delivery assembly is adapted to provide water to respiratory gases passing through the housing over time. The water delivery assembly may include a liquid water reservoir and a hollow tubular member including a first end in fluid communication with the liquid water reservoir and an opposing open second end exposed to respiratory gases passing through the housing. The liquid water reservoir preferably is adapted to be refillable while the housing is connected to the tracheal tube device.
Each individual feature and each combination of two or more features described herein are included within the scope of the present invention provided that the features included in the combination are not mutually inconsistent.
Commonly assigned U.S. patent application Ser. No. 09/113,649 filed on Jul. 10, 1998 herewith discloses additional features which can be used in combination with the present apparatus. The disclosure of this application, in its entirety, is incorporated by reference herein.
These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.